Embodiments of the present invention relate generally to power transfer systems, and, in particular, to resonance based contactless power transfer systems.
In certain applications where instantaneous or continuous energy transfer is needed but interconnecting wires are inconvenient, contactless power transfer is desirable. One contactless power transfer method is an electromagnetic induction method that works on the principle of a primary transformer coil generating a dominant magnetic field and a secondary transformer coil in the vicinity of the primary transformer coil generating a corresponding voltage. The magnetic field received by the secondary transformer coil decreases as a function of the square of the distance between the two coils, and hence the coupling between primary and secondary coils is weak for distances greater than a few millimeters.
Another method of contactless power transfer attempts to increase the efficiency of the inductive power transfer by resonant inductive coupling. Transmitter and receiver elements resonate at the same frequency, and maximum induction occurs at the resonant frequency. However, such resonant induction is sensitive to load and gap variations.
There is a need for an efficient contactless power transfer system that may operate with coils separated by longer distances than are presently acceptable and is efficient when subjected to misalignment or load variations. Further, there is a need for accommodating and efficient materials having high dielectric properties and low dielectric loss factors, and robust design that can be cost effectively manufactured and used in the power transfer systems for the required frequency ranges.